The DisplayPort architecture, promulgated by the Video Electronics Standards Association (VESA), utilizes a link layer that implements a link service. It is one of many types of communications protocols that implement link services. The link service in DisplayPort and within a source device is used to discover, configure and maintain a link with a device which it connects to. The link service configures the link through what is known as link training. Link training is a process where different control settings are adjusted at a source and destination until the quality of the signal in training is optimized and matched between the source and receiver. These settings affect the electrical properties (the strength and shape) of a transmitted signal and how the signal is read at the receiver. The training process is controlled through handshaking between the DisplayPort transmitter (graphics output) and receiver (repeater, hub, or display) over an auxiliary channel. Link Training is an iterative process. Combinations of number of signal lanes and signal speeds may be tried as part of the training sequence. A satisfactory result delivers a transmitter and receiver tuned to each other for accurate signal transmission. It is possible that the training results deliver a tuned result that is not optimized but instead is set near the edge of acceptable levels. In such cases, the receiver may occasionally miss signals due to noise on the lines or other factors that negatively impact the signal quality. As a result, the receiver is more likely to lose synchronization with the source which can result in screen flicker and loss of signal which results in a loss of the display image.
The specification for DisplayPort indicates that once a signal is successfully received during the training sequence, an additional adjustment should be done either at the source or destination to add additional fidelity. It has been found that, in practice, such a final adjustment is not always performed. Accordingly, the signal quality may be potentially on the edge of the optimal settings for best margin which results in potential signal loss periodically.
Furthermore, the operation of the final training adjustment(s) is controlled by the firmware within the receiver (display). Such firmware is often set at the factory and is not readily updatable post production.
Accordingly, there exists a need for a device and method for improving signal link quality between devices which utilize link training such as, for example, in DisplayPort signals.